The present invention relates to improvements in drilling bits for use in drilling wells in the ground, such as water wells or oil wells.
Conventional drill bits are made of a plurality of sectional body parts together making up a circular bit assembly. Each body part has a cutter rotatably mounted thereon, with the axis of rotation oriented toward the center of the bit assembly. As the bit assembly is rotated, the individual cutters rotate on their respective body parts to scour and loosen the earth.
Various bit assemblies have been devised, as indicated by the following U.S. patents:
U.S. Pat. No. 2,011,084 to F. L. Scott;
U.S. Pat. No. 2,154,032 to A. C. Catland;
U.S. Pat. No. 2,297,192 to C. E. Reed;
U.S. Pat. No. 2,351,357 to E. L. Miller et al.;
U.S. Pat. No. 2,470,695 to J. S. Goodwin et al.;
U.S. Pat. No. 3,095,934 to R. E. Goetz;
U.S. Pat. No. 3,950,041 to R. A. Miglierini;
U.S. Pat. No. 4,298,079 to G. Norlander et al.
These patents disclose various bearing assemblies which are intended to handle the frictional forces developed in the bit during drilling. The frictional forces have two force components acting on the bit. Axial components are usually handled by ball bearings, and radial components are usually handled by roller bearings. The radial force components are generally quite large because the net downward movement of the drill into the ground is resolved substantially entirely into a radial force on each body part and cutter assembly.
The radial forces are so large that excessive wear of the roller bearings is a major cause of early bit failure. Often the bearings are worn to the point that the cutter falls off of the body part while in the hole in the ground, although the teeth of the cutter still have a substantial useful life. As a result it has been necessary to remove the entire drilling assembly, fish the cutter out of the hole, reassemble the bit, and then reinsert the drilling assembly before drilling can continue. This substantial downtime is costly.